What do some photosynthetic bacteria use as a source of electrons instead of water? a. oxygen (O2) b. hydrogen sulfide (H2S) c. organic compounds (e.g., CH3COO−) d. nitrate (NO3-)

What does the chemiosmotic hypothesis claim? a. ATP is generated using phosphates taken from intermediates in the electron transport chain. b. ATP is generated using a phosphate gradient produced by glycolysis and the citric acid cycle. c. ATP is generated using a proton-motive force that is produced by the electron transport chain. d. Water is generated using electrons taken from NADH and FADH2 and transported through the electron transport chain.

What are organisms called that use inorganic compounds as electron donors in cellular respiration? a. phototrophs b. heterotrophs c. organotrophs d. lithotrophs

Unlike plant cell walls that contain cellulose, bacterial cell walls are composed of          .

Explain how feedback inhibition regulates metabolic pathways.

Evaluate these statements about Koch's postulates, which are used to establish a causative link between a specific microbe and a specific disease. Select True or False for each statement. T/F The microbe must be present in individuals suffering from the disease and absent from healthy individuals. T/F The microbe must be isolated and grown in pure culture. T/F If organisms from the pure culture are injected into a healthy experimental animal, the disease symptoms should appear. T/F The microbe does not have to be isolated from the experimental animal as long as the disease is present.

What has metagenomic analysis allowed researchers to do for the first time? a. sample organisms from an environment and grow them under defined conditions in the lab b. isolate organisms from an environment and sequence their entire genome c. study organisms that cannot be cultured (grown in the lab) d. identify important morphological differences among species

Biologists often use the term 'energy source' as a synonym for 'electron donor.' Why?

Using what you have learned about changes in Gibbs free energy, would you predict the ∆G value of catabolic reactions to be positive or negative? What about anabolic reactions? Justify your answers using the terms 'enthalpy' and 'entropy.'

Cyanide (C≡N−) blocks complex IV of the electron transport chain. Suggest a hypothesis for what happens to the ETC when complex IV stops working. Your hypothesis should explain why cyanide poisoning in humans is fatal.

Streptococcus mutans obtains energy by oxidizing sucrose. This bacterium is abundant in the mouths of Western European and North American children and is a prominent cause of cavities. The organism is virtually absent in children from East Africa, where tooth decay is rare. Propose a hypothesis to explain this observation. Outline the design of a study that would test your hypothesis.

Suppose that you've been hired by a firm interested in using bacteria to clean up organic solvents found in toxic waste dumps. Your new employer is particularly interested in finding cells that are capable of breaking a molecule called benzene into less-toxic compounds. Where would you go to look for bacteria that can metabolize benzene as an energy or carbon source? How would you design an enrichment culture capable of isolating benzene-metabolizing species?

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

What conclusions can be drawn regarding the impact of FMT from depressed individuals on behaviors associated with depression and anxiety in rats?

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

What conclusion can be drawn regarding the relationship between microbiome diversity and mental health in rats?

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

Why was it important for the rats used in the study to be free of gut microbiota to begin with?

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

Patients from the depression group had relatively high levels of bacteria in the genus Paraprevotella (a Gram-negative bacterium) relative to the control group of patients. Which of the following is a structural difference between Paraprevotella and methicillin-resistant Staphylococcus aureus (MRSA), a Gram-positive bacterium?

a. Paraprevotella contains a thick layer of peptidoglycan in its cell wall and MRSA lacks peptidoglycan.

b. The plasma membrane of Paraprevotella is surrounded by a cell wall that contains a relatively thin layer of peptidoglycan and an outer membrane and MRSA cells are surrounded by cell walls with a relatively thick layer of peptidoglycan,

c. Paraprevotella produces endospores but MRSA does not.

d. Paraprevotella lacks a plasma membrane but MRSA cells are surrounded by two plasma membranes.

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

Hypothesize how bacteria living in a person’s gut might influence events occurring in the brain.

Researchers examined the relationship between gut microbiomes and depression. To do so, they collected fecal samples from people with depression and also a control group of individuals with no signs of depression. They then performed a fecal microbiota transfer (FMT) by adding the samples to rats that had no gut microbiota and examined behaviors associated with depression and anxiety as well as species of bacteria that ended up growing in the rats’ guts. The results are presented below. Graph (a) shows the rats’ interest in a pleasurable experience (drinking sugar water). Graph (b) shows the amount of time rats spent out in the open versus along the edge of an area (a sign of anxiety). Graph (c) shows the number of species observed in rats after FMT.

Probiotics are often marketed as a food or supplement that can help promote a healthy gut. How might a healthy gut microbiome help improve mental health?